Pages: 1 [2]   Go Down
Author Topic: Wire library enables internal pull-ups -> bad for 3.3V I2C devices.  (Read 2719 times)
0 Members and 1 Guest are viewing this topic.
Global Moderator
Offline Offline
Brattain Member
*****
Karma: 474
Posts: 18696
Lua rocks!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

There would be a bit of a danger if a 3.3V I2C device lets the line go high (by going high impedance) the line will only reach 3.3V if you pull-up to 3.3V and not 5V. Thus, although the Atmega running at 5V will read that as a high, it is only just (it registers high at above 2.7V) - page 412 of datasheet. You would need a reasonably powerful (ie. low) pull-up resistor to make sure it reached that level quickly enough.
Logged

Pages: 1 [2]   Go Up
Jump to: